Some feel that the Nether is hard enough. I say its not rewarding enough. This reward would be found at a new structure, The Nether Gate (New Nether/Overworld Dungeon), and guarding this new structure would be the nether's new big bad mini boss, "The Gate Keeper!"
The Gate Keeper spawns on a patch of soul sand on the floor of the structure when the player approaches.
Imagine a large thick boned wither skeleton-like mob the size of a mutant skeleton. Now give it black ram horns. Now put it in nether-portal-purple armor comprised of refined obsidian covering his shins, upper arms, chest (rib cage), and a helmet similar to a Spartan's helm. Now put infinite darkness where the face would be seen in the helmet. Give it 6 spine-like bone tentacles coming out of its back Giratina style. And finally give it its signature mace, Shield Breaker. Link Here: The Mace (Shield Breaker)
Now you have the guard of the gate of the nether world. The mighty centurion! "The Gate Keeper!"
The gate keeper could have a small series of different attacks:
1. Swings it's mace causing knock-back and heavy damage to player's armor/shield (Read the link about the mace above for more info on that)
2. Like Evoker summons four mobs from the ground, Magma Worms, which arch outwards like a dolphin in four different directions burning anything they come in contact with and then swiftly despawn.
3. Rises into the air like a blaze and summons arrows of wither to throw at players. (one arrow for each of the six bone tentacles on its back)
Once you defeat The Gate Keeper it will have a high chance of dropping it's mace, "Shield Breaker!" And the player will be free to explore what the Keeper was guarding. (Note: I call the mace "Shield Breaker" for dramatic effect. In game it would probably just be known as "Mace")
Remember to Vote if you'd like to see The Gate Keeper added in the Fan Update!